An openable roof or an openable wall usually consists of two or more panels, which are displaceable relative to each other along guide rails between an open and a closed state. Because the panels are suspended from guide rails there are a number of junctions and joints through which air, moisture and dirt, such as dust and pollen, are able to penetrate. As a rule the moisture and dirt are caused by wind and weather, but may also be a consequence of maintenance activities such as window cleaning. Moisture may also accumulate in the form of a condensate, which is due to the natural moisture content of the atmosphere. No matter how the moisture penetrates into junctions and joints, it causes the formation of condensate and discoloration, which affects visibility and the overall visual appearance as well as the material in itself in the form of corrosion and aging. Moreover, the moisture binds dirt, which necessitates regular maintenance.
A particular area associated with the risk of air and dirt penetrating due to wind and weather is the zone of overlap between two panels. This zone forms an air pocket which is closed along three edge portions of the two overlapping panels, but which opens onto the surroundings along a fourth edge portion, and more specifically into the open air on the outside of the roof/wall. Under windy conditions water/snow or dirt may be blown into the air pocket, which is similar to a wind catcher. By using various seals the air and the moisture/dirt are prevented from penetrating further between the two panels. A sealing system of this kind is disclosed in U.S. Pat. No. 5,829,204, in which the air pocket is delimited along three edges by seals arranged between two overlapping roofing panels.
Yet, penetration cannot be prevented altogether, since some leakage will always occur due to the capillary action between the individual seal and the surface against which it seals. Furthermore, leakage occurs through the gap that is inevitably formed between the individual seal and the surface against which it seals as the wind blows into the air pocket. This is because the wind causes a cyclic deflection of the upper, outermost panel relative to the lower, inner panel in the form of a lifting motion transversely of the latitudinal direction of the panels. The lifting motion causes a gap to form in the sealing surface between the two panels, through which air, moisture and dirt may enter, thereby penetrating further into the guide rails. Once the moisture is inside the guide rails there is no natural way for it to escape. To eliminate the risk of this type of wind-related deflection and moisture penetration, the extent of the panels in the transverse direction is usually limited and the surface instead divided into several sections. This means that more panels and more guide rails are required, which makes the roof or wall more expensive and less aesthetically appealing. Furthermore, it will be appreciated that by providing tighter surfaces gains in the form of lower heating costs for the premises can be achieved.